The matrices now used for the reconstruction of angular made of aluminum alloys or of aluminum, exhibit two drawbacks. In the first place, the operation of "shaping" the matrix is laborious to make it correspond to the shape of the tooth on which the work is being performed: this operation is most often performed manually by the dentist, by making a plastic deformation of the matrix; in the second place, a fact still more disadvantageous, the matrices of aluminum or metals with similar mechanical characteristics necessarily cannot be transparent, and consequently preclude the use of photopolymerizable composite resins, which recently have increased their field of application thanks to the values and advantages they offer. But many matrices of transparent synthetic material in use today, while avoiding this latter drawback, comprise a very laborious intervention since the dentist has to hold them with his fingers in a suitable position to give a correct shaping to the resins used for the reconstruction, and at the same time to avoid shielding, with the fingers themselves, the radiations emitted by the lamps for photopolymerization of the said resins. Most of the time, this is a great problem.
Still there are also devices comprising forceps and an angular matrix of transparent material: generally two peduncles are applied on the two opposite sides of the matrix to hold the matrix in position, peduncles dimensioned to be able to be inserted in holes or notches made on the ends of forceps. But this solution also exhibits notable laboriousness and inconvenience due to the objective difficulty of keeping the forceps joined to the peduncles, exerting at the same time on the matrix the thrust, necessarily very delicate, suitable for keeping it in the desired position in the course of the operation.